<!DOCTYPE HTML>
<html>
    <head>
        <title>Example</title>
        <style>
            canvas {border: thin solid black}
            body > * {float:left;}
        </style>
    </head>
    <body>
        <canvas id="canvas" width="500" height="140">
            Your browser doesn't support the <code>canvas</code> element
        </canvas>
        <script>
            var ctx = document.getElementById("canvas").getContext("2d");

            var point1 = [100, 10];
            var point2 = [200, 10];
            var point3 = [200, 110];

            ctx.fillStyle = "yellow";
            ctx.strokeStyle = "black";
            ctx.lineWidth = 4;

            ctx.beginPath();
            ctx.moveTo(point1[0], point1[1]);
            ctx.arcTo(point2[0], point2[1], point3[0], point3[1], 100);
            ctx.stroke();
    
            drawPoint(point1[0], point1[1]);
            drawPoint(point2[0], point2[1]);
            drawPoint(point3[0], point3[1]);
    
            ctx.beginPath();
            ctx.moveTo(point1[0], point1[1]);
            ctx.lineTo(point2[0], point2[1]);
            ctx.lineTo(point3[0], point3[1]);
            ctx.stroke();
    
            function drawPoint(x, y) {
                ctx.lineWidth = 1;
                ctx.strokeStyle = "red";
                ctx.strokeRect(x -2, y-2, 4, 4);
            }
        </script>
    </body>
</html>
